Metal surface treatment liquid for cation electrodeposition coating

ABSTRACT

A surface treatment with a zirconium ion that enables sufficient throwing power, and superior anti-corrosion properties to be exhibited when thus surface treated metal base material is subjected to cation electrodeposition coating is provided. A metal surface treatment liquid for cation electrodeposition coating includes zirconium ions and tin ions, and has a pH of 1.5 to 6.5, in which: the concentration of zirconium ions is in the range of 10 to 10,000 ppm; and the content of the tin ions to the zirconium ions is 0.005 to 1 on a mass basis. Furthermore, a polyamine compound, copper ions, fluorine ions, and a chelate compound may also be included.

CROSS-REFERENCE TO RELATED APPLICATION(S)

The present application is a continuation of PCT application no.PCT/JP2007/074536 filed Dec. 20, 2007.

TECHNICAL FIELD

The present invention relates to a metal surface treatment liquid,particularly to a metal surface treatment liquid suited for cationelectrodeposition coating, and a method of metal surface treatment.

BACKGROUND ART

In order to impart anti-corrosion properties to various metal basematerials, surface treatments have thus far been performed.Particularly, a zinc phosphate treatment has been generally employed onmetal base materials which constitute automobiles. However, this zincphosphate treatment has a problem of sludge generation as a by-product.Accordingly, a surface treatment without use of zinc phosphate for anext generation has been demanded, and a surface treatment withzirconium ions is one of such treatments (see, for example, PatentDocument 1).

Meanwhile, metal base materials which constitute automobiles andnecessitate high anti-corrosion properties are subjected to cationelectrodeposition coating following the surface treatment. The cationelectrodeposition coating is carried out on the grounds that the coatedfilm obtained by cation electrodeposition coating has superioranti-corrosion properties, and it has “throwing power”, generallyreferred to, that is a property of allowing automobile bodies having acomplicated shape to be completely coated.

However, it has been recently proven that when a metal base materialwhich had been surface treated with the zirconium ions is subjected tothe cation electrodeposition coating, there may be a case in which nosignificant effect in terms of the throwing power is achieved, forexample, the throwing power may not be sufficient for cold-rolled steelplates in some cases. Accordingly, when the cation electrodepositioncoating is carried out, sufficient anti-corrosion properties cannot beachieved if the throwing power is insufficient.

Patent Document 1: Japanese Unexamined Patent Application PublicationNo. 2004-218070

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

An object of the present invention is to provide a surface treatmentwith zirconium ions that enables sufficient throwing power and exhibitsuperior anti-corrosion properties to be exhibited, when thus surfacetreated metal base material is subjected to cation electrodepositioncoating.

Means for Solving the Problems

Aspects of the present invention are as follows. In a first aspect ofthe present invention, a metal surface treatment liquid for cationelectrodeposition coating contains zirconium ions, and tin ions, and hasa pH of in the range of 1.5 to 6.5, in which: the concentration of thezirconium ions is in the range of 10 to 10,000 ppm; and theconcentration ratio of the tin ions to the zirconium ions is 0.005 to 1on a mass basis.

In a second aspect of the present invention, a metal surface treatmentliquid for cation electrodeposition coating according to the firstaspect further includes a polyamine compound.

In a third aspect of the present invention, a metal surface treatmentliquid for cation electrodeposition coating according to the first orsecond aspect further includes copper ions.

In a forth aspect of the present invention, a metal surface treatmentliquid for cation electrodeposition coating according to any one of thefirst to third aspects further includes fluorine ions, in which theamount of free fluorine ions at a pH of 3.0 is the range of 0.1 to 50ppm.

In a fifth aspect of the present invention, a metal surface treatmentliquid for cation electrodeposition coating according to any one of thefirst to forth aspects further includes a chelate compound.

In a sixth aspect of the metal surface treatment liquid for cationelectrodeposition coating according to the fifth aspect of the presentinvention, the chelate compound is sulfonic acid.

In a seventh aspect of the present invention, a metal surface treatmentliquid for cation electrodeposition coating according to any one of thefirst to sixth aspects further includes an oxidizing agent.

In an eighth aspect of the present invention, a metal surface treatmentliquid for cation electrodeposition coating according to any one of thefirst to seventh aspects further includes at least one ions selectedfrom the group consisting of aluminum ions and indium ions.

In a ninth aspect of the present invention, a method of metal surfacetreatment includes a step of subjecting a metal base material to asurface treatment with the metal surface treatment liquid for cationelectrodeposition coating according to any one of the first to eighthaspects.

In a tenth aspect of the present invention, a metal base materialincludes a coating film formed by a surface treatment obtained by themethod of metal surface treatment according to the ninth aspect.

In an eleventh aspect of the present invention, a metal base materialincluding a coating film having an element ratio of zirconium/tin on amass basis being 1/10 to 10/1 formed on the metal base materialaccording to the tenth aspect.

In a twelfth aspect of the present invention, a method of cationelectrodeposition coating includes: the step of subjecting a metal basematerial to a surface treatment with the metal surface treatment liquidfor cation electrodeposition coating according to any one of the firstto eighth aspects; and a step of subjecting the surface treated metalbase material to cation electrodeposition coating.

In a thirteenth aspect of the present invention, a metal base materialcoated by the cation electrodeposition is obtained with the method ofcation electrodeposition coating according to the twelfth aspect.

Accordingly, the metal surface treatment liquid for cationelectrodeposition coating of the present invention is a chemicalconversion treatment liquid containing zirconium ions and tin ions, andhaving a pH in the range of 1.5 to 6.5, in which the concentration ofzirconium ions in the range of 10 to 10,000 ppm, and the content of thetin ions with respect to the zirconium ions is 0.005 to 1 on a massbasis. Moreover, the metal surface treatment liquid for cationelectrodeposition coating may further contain a polyamine compound,copper ions, fluorine ions, a chelate compound, an oxidizing agent, anda rust-preventive agent. When the fluorine ions are included, the amountof free fluorine ions at a pH of 3.0 may be 0.1 to 50 ppm.

The method of metal surface treatment of the present invention includesthe step of subjecting a metal base material to a surface treatment withthe abovementioned metal surface treatment liquid.

A coating film obtained by the surface treatment is formed on thesurface treated metal base material of the present invention. Theelement ratio of zirconium/tin on mass basis in the coating film may be1/10 to 10/1.

The method of cation electrodeposition coating of the present inventionincludes a step of subjecting a metal base material to a surfacetreatment with the abovementioned metal surface treatment liquid, and astep of subjecting the surface treated metal base material to cationelectrodeposition coating.

The metal base material coated by the cation electrodeposition of thepresent invention is obtained by the abovementioned method of coating.

EFFECTS OF THE INVENTION

It is believed that the throwing power attained by the metal surfacetreatment liquid for cation electrodeposition coating of the presentinvention can be improved by including tin ions in addition to zirconiumions when the cation electrodeposition coating is carried out afterforming a conversion coating film with this treatment liquid. Althoughnot clarified, the grounds are conceived as follows.

When zirconium ions are used alone, formation of their oxide coatingfilm is believed to be executed simultaneously with etching of the metalbase material in an acidic medium. However, since segregation materialsand the like of compounds containing silicon or carbon in addition tosilica may be present on cold-rolled steel plates, such parts are notsusceptible to etching. Therefore, the coating film cannot be uniformlyformed with zirconium oxide, whereby portions without coating filmformation can be present. Since a difference in electric current flow isbelieved to be generated between the parts with and without formation ofthe coating film, the electrodeposition is not uniformly executed, andconsequently, the throwing power cannot be sufficiently attained.

When tin ions are additionally present, it is further considered as inthe following. Since the tin ions are less likely to be affected on thesteel plate as compared with the zirconium ions, their oxide coatingfilm can be more easily formed on the base material. Although formationof the coating film of the tin ions is not specific to the parts wherethe zirconium ions are not significantly deposited, formation of theoxide coating film of the tin ions is not restricted to a specific partwhile having another part remain without formation of the film. As aresult, the tin ions would form the coating film such that it covers thepart where the zirconium ion could not form the coating film.

The metal surface treatment liquid for cation electrodeposition coatingof the present invention can improve adhesiveness to the coated film bycation electrodeposition through including the polyamine compound, andconsequently, it can pass SDT test under more stringent conditions. Inaddition, the metal surface treatment liquid for cationelectrodeposition coating of the present invention can improveanti-corrosion properties by including the copper ion. Although thegrounds are not clarified, it is believed that some interaction may becaused between copper and zirconium in forming the coating film.Furthermore, the metal surface treatment liquid for cationelectrodeposition coating of the present invention can form a zirconiumoxide coating film in a stable manner by including a chelate compoundwhen a metal other than zirconium is included in large quantity. Thisoccurrence is believed to result from capture by the chelate compound ofmetal ions that are more likely to be deposited than zirconium.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a perspective view illustrating one example of the box foruse in evaluating the throwing power; and

FIG. 2 shows a view schematically illustrating evaluation of thethrowing power.

PREFERRED MODE FOR CARRYING OUT THE INVENTION

The metal surface treatment liquid for cation electrodeposition coatingof the present invention is a chemical conversion treatment liquid thatcontains zirconium ions and tin ions, and has a pH in the range of 1.5to 6.5.

The zirconium ions are included at a concentration in a range of 10 to10,000 ppm. When the concentration is less than 10 ppm, sufficientanti-corrosion properties cannot be achieved since deposition of thezirconium coating film is not enough. In addition, even though theconcentration may exceed 10,000 ppm, an effect to justify the amountcannot be exhibited since the deposition amount of the zirconium coatedfilm is not increased, and adhesiveness of the coated film may bedeteriorated, thereby leading to inferior anticorrosion performance suchas those in SDT. The lower limit and the upper limit of theconcentration are preferably 100 ppm and 500 ppm, respectively.

The concentration of the metal ions herein, when a complex or oxidethereof was formed, is represented by the concentration based on themetal element, taking into account only of the metal atom in the complexor oxide. For example, the concentration based on the metal element ofzirconium of 100 ppm complex ions ZrF₆ ²⁻ (molecular weight: 205) iscalculated to be 44 ppm by the formula of 100×(91/205). In the metalsurface treatment liquid for cation electrodeposition coating of thepresent invention, the metal compound (zirconium compound, tin compound,copper compound and other metal compounds) is included at just a slightproportion, if present, in the state of a nonionic state such as anoxide portion, and is believed to be present almost in the form of themetal ion. Therefore, the metal ion concentration referred to herein is,irrespective of the presence in the form of the nonionic portion, themetal ion concentration when it is assumed to be present as the metalion dissociated at a level of 100%.

The tin ion included in the metal surface treatment liquid for cationelectrodeposition coating of the present invention is preferably abivalent cation. When the tin ion has other valence, the intended effectmay not be exhibited. However, the tin ion is not limited to thebivalent cation, but can be used in the present invention as long as itcan be deposited on the metal base material. For example, when the tinions form a complex, it may be a quadrivalent cation, which can also beused in the present invention. The concentration of the tin ions is0.005 to 1 on a mass basis with respect to the concentration of thezirconium ions. When the ratio is less than 0.005, the effect byaddition is not exhibited, while zirconium may not be significantlydeposited when the ratio exceeds 1. The lower limit and the upper limitof the concentration are preferably 0.02 and 0.2, respectively. However,when the total amount of the zirconium ion and tin ion is too small, theeffect of the present invention may not be exhibited. Therefore, thetotal concentration of the zirconium ion and the tin ion in the metalsurface treatment liquid of the present invention is preferably no lessthan 15 ppm.

The content of the tin ions in the metal surface treatment liquid of thepresent invention is preferably is preferably 1 to 100 ppm. When thecontent is less than 1 ppm, deposition of tin at the portion wherezirconium could not form the coating film may be insufficient, and theanti-corrosion properties such as those in SDT are likely to beinferior. When the content exceeds 100 ppm, deposition of the zirconiumcoating film may be difficult, whereby the anti-corrosion properties andthe coating appearance are likely to be inferior. The concentration ismore preferably 5 to 100 ppm, and still more preferably 5 to 50 ppm.

The metal surface treatment liquid for cation electrodeposition coatingof the present invention has a pH in the range of 1.5 to 6.5. When thepH is less than 1.5, the metal base material cannot be sufficientlyetched to decrease the coating film amount, and sufficientanti-corrosion properties cannot be achieved. In addition, the stabilityof the treatment liquid may not be sufficient. In contrast, when the pHis higher than 6.5, excessive etching may lead to failure in formationof sufficient coating film, or an un-uniform adhesion amount and filmthickness of the coating film may adversely affect the coatingappearance and the like. The lower limit and the upper limit of pH arepreferably 2.0 and 5.5, and still more preferably 2.5 and 5.0,respectively.

The metal surface treatment liquid for cation electrodeposition coatingof the present invention may further include a polyamine compound forimproving adhesiveness to the coated film by cation electrodepositionwhich is formed after the surface treatment. The polyamine compound usedin the present invention is believed to be fundamentally significant inbeing an organic molecule having an amino group. Although speculative,the amino group is believed to be incorporated in the coating film by achemical action with zirconium oxide deposited as a coating film on themetal base plate, or with the metal base plate. In addition, thepolyamine compound that is an organic molecule is believed to beresponsible for adhesiveness with the coated film provided on the metalbase plate having the coating film formed thereon. Therefore, when thepolyamine compound that is an organic molecule having an amino group isused, adhesiveness between the metal base plate and the coated film issignificantly improved, and superior corrosion resistance can beattained. Examples of the polyamine compound include hydrolysiscondensates of aminosilane, polyvinylamine, polyallylamine, watersoluble phenolic resins having an amino group, and the like. Since theamount of amine can be freely adjusted, the hydrolysis condensate ofaminosilane is preferred. Therefore, exemplary metal surface treatmentliquids for cation electrodeposition coating of the present inventioninclude, for example, the metal surface treatment liquids for cationelectrodeposition coating which contain zirconium ions, tin ions, and ahydrolysis condensate of aminosilane; the metal surface treatmentliquids for cation electrodeposition coating which contain zirconiumions, tin ions, and polyallylamine; and the metal surface treatmentliquids for cation electrodeposition coating which contain zirconiumions, tin ions, and a water soluble phenolic resin having an aminogroup. In addition, these metal surface treatment liquids for cationelectrodeposition coating may contain fluorine as described later.

The hydrolysis condensate of aminosilane is obtained by carrying outhydrolysis condensation of an aminosilane compound. Examples of theaminosilane compound include vinyltrichlorosilane,vinyltrimethoxysilane, vinyltriethoxysilane, 2-(3,4epoxycyclohexyl)-ethyltrimethoxysilane,3-glycidoxypropyltrimethoxysilane,3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropyltriethoxysilane,p-styryltrimethoxysilane, 3-methacryloxypropylmethyldimethoxysilane,3-methacryloxypropyltrimethoxysilane,3-methacryloxypropylmethyldiethoxysilane,3-methacryloxypropyltriethoxysilane, 3-acryloxypropyltrimethoxysilane,N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane,N-2-(aminoethyl)-3-aminopropyltrimethoxysilane,N-2-(aminoethyl)-3-aminopropyltriethoxysilane,3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane,3-triethoxysilyl-N-(1,3-dimethyl-butylidene)-propylamine,N-phenyl-3-aminopropyltrimethoxysilane,N-(vinylbenzyl)-2-aminoethyl-3-aminopropyltrimethoxysilanehydrochloride, 3-ureidepropyltriethoxysilane,3-chloropropyltrimethoxysilane, 3-mercaptopropylmethyldimethoxysilane,3-mercaptopropyltrimethoxysilane, bis(triethoxysilylpropyl)tetrasulfide,and 3-isocyanate propyltriethoxysilane, which are silane coupling agentshaving an amino group. In addition, examples of commercially availableproducts which can be used include “KBM-403”, “KBM-602”, “KBM-603”,“KBE-603”, “KBM-903”, “KBE-903”, “KBE-9103”, “KBM-573”, “KBP-90” (alltrade names, manufactured by Shin-Etsu Chemical Co.,), “XS1003” (tradename, manufactured by Chisso Corporation), and the like.

The hydrolytic condensation of the aforementioned aminosilane can becarried out by a method well known to persons skilled in the art.Specifically, the hydrolytic condensation can be carried out by addingwater required for hydrolysis of the alkoxysilyl group to at least onekind of aminosilane compound, and stirring the mixture while heating asneeded. The degree of condensation can be regulated with the amount ofwater used.

A higher degree of condensation of aminosilane hydrolysis condensate ispreferred, since in this case where zirconium is deposited as an oxide,the above aminosilane hydrolysis condensate tends to be easilyincorporated therein. For example, the portion on a mass basis of dimeror higher-order multimers of aminosilane in the total amount of theaminosilane is preferably no less than 40%, more preferably no less than50%, still more preferably no less than 70%, and even more preferably noless than 80%. Therefore, when aminosilane is allowed to react in ahydrolytic condensation reaction, it is preferred to permit the reactionunder conditions in which aminosilane is more likely to be hydrolysedand condensed such as those in which an aqueous solvent containing acatalyst such as acetic acid and alcohol is used as the solvent. Inaddition, by allowing for a reaction under conditions with acomparatively high aminosilane concentration, a hydrolysis condensatehaving a high degree of condensation is obtained. Specifically, it ispreferred to allow for the hydrolytic condensation at an aminosilaneconcentration falling within the range of 5% by mass to 50% by mass. Thedegree of condensation can be determined by ²⁹Si—NMR measurement.

As the polyvinylamine and polyallylamine, commercially availableproducts can be used. Examples of polyvinylamine include “PVAM-0595B”(trade name, manufactured by Mitsubishi Chemical Corporation) and thelike, and examples of the polyallylamine include “PAA-01”, “PAA-10C”,“PAA-H-10C”, “PAA-D-41HCl” (all trade names, manufactured by NittoBoseki Co., Ltd.) and the like.

The molecular weight of the polyamine compound is preferably in therange of 150 to 500,000. When the molecular weight is less than 150, aconversion coating film having sufficient adhesiveness may not beobtained. When the molecular weight exceeds 500,000, formation of thecoating film may be inhibited. The lower limit and the upper limit aremore preferably 5,000 and 70,000, respectively. When the polyaminecompound has the amino group in too large an amount, it may adverselyinfluence the coating film, while the effect to improve the adhesivenesswith the coating film provided by the amino group is not significantlyachieved when the amount is too small. Therefore, the polyamine compoundpreferably has a primary and/or secondary amino group of no less than0.1 mmol and no more than 17 mmol per gram of the solid content, andmore preferably a primary and/or secondary amino group of no less than 3mmol and no more than 15 mmol per gram of the solid content.

The number of moles of the primary and/or secondary amino group per gramof the solid content of the polyamine compound can be determinedaccording to the following formula (I).

Amount of Amino Group=(mX−nY)/(m+n)  Formula (1)

in which the mass ratio of solid contents of the polyamine compound andthe compound having a functional group A and/or a functional group B isdefined as m:n; the number of mmoles of the functional group A and/orthe functional group B per gram of the compound having the functionalgroup A and/or the functional group B is defined as Y; and the number ofmmoles of the primary and/or secondary amino group included per gram ofthe polyamine compound when the compound having the functional group Aand/or the functional group B is not included in the composition for themetal surface treatment is defined as X.

The content of the polyamine compound in the metal surface treatmentliquid for cation electrodeposition coating of the present invention canbe in the range of 1 to 200% based on mass of the zirconium metalincluded in the surface treatment liquid. When the content is less than1%, the intended effect cannot be exhibited, while the content exceeding200% may lead to failure in sufficient formation of the coating film.The upper limit of the content is more preferably 120%, more preferably100%, still more preferably 80%, and even more preferably 60%.

The metal surface treatment liquid for cation electrodeposition coatingof the present invention may further contain a copper ion for improvingthe anti-corrosion properties. With respect to the amount of the copperions, the concentration preferably accounts for 10 to 100% with respectto the concentration of the tin ions. When the concentration is lessthan 10%, the intended effect may not be exhibited, while deposition ofzirconium may be difficult, similarly to the case of the tin ions whenit exceeds the concentration of the tin ions. Exemplary metal surfacetreatment liquids for cation electrodeposition coating of the presentinvention include, for example, the metal surface treatment liquids forcation electrodeposition coating which contain zirconium ions, tin ionsand copper ions. In this case, the fluorine ions described later can befurther included and the aforementioned polyamine compound can beincluded.

It is preferred that the metal surface treatment liquid for cationelectrodeposition coating of the present invention contains fluorineions. Since the concentration of the fluorine ions varies depending onthe pH, the amount of free fluorine ions is defined at a specified pH.In the present invention, the amount of the free fluorine ions at a pHof 3.0 is in the range of 0.1 to 50 ppm. When the amount is less than0.1 ppm, the metal base material cannot be sufficiently etched so thatthe coating film amount is decreased, and sufficient anticorrosionproperties cannot be achieved. In addition, the treatment liquid may nothave enough stability. In contrast, when the amount is above 50 ppm,excessive etching may lead to failure in formation of sufficient coatingfilm, or an un-uniform adhesion amount and film thickness of the coatingfilm may adversely affect the coating appearance and the like. The lowerlimit and the upper limit are preferably 0.5 ppm and 10 ppm,respectively. Exemplary metal surface treatment liquids for cationelectrodeposition coating of the present invention include, for example,the metal surface treatment liquids for cation electrodeposition coatingwhich contain zirconium ions, tin ions, and fluorine ions.

The metal surface treatment liquid for cation electrodeposition coatingof the present invention may include a chelate compound. By includingthe chelate compound, deposition of metals other than zirconium can besuppressed in the treatment liquid, and the coating film of zirconiumoxide can be stably formed. As the chelate compound, amino acid,aminocarboxylic acid, a phenolic compound, aromatic carboxylic acid,sulfonic acid, ascorbic acid and the like can be exemplified. Carboxylicacid having a hydroxyl group such as citric acid and gluconic acid,conventionally known as chelating agents, cannot exert their functionenough in the present invention.

As the amino acid, a variety of naturally occurring amino acids andsynthetic amino acids, as well as amino acids having at least one aminogroup and at least one acid group (carboxyl group, sulfonic acid groupor the like) in one molecule, can be extensively utilized. Among these,at least one selected from the group consisting of alanine, glycine,glutamic acid, aspartic acid, histidine, phenylalanine, asparagine,arginine, glutamine, cysteine, leucine, lysine, proline, serine,tryptophan, valine and tyrosine, and a salt thereof can be preferablyused. Furthermore, when there is an optical isomer of the amino acid,any one can be suitably used irrespective of the forms, i.e., L-form,D-form, or racemic bodies.

In addition, as the aminocarboxylic acid, a compound having bothfunctional groups, an amino group and a carboxyl group in one moleculeother than the amino acid described above can be extensively used. Amongthese, at least one selected from the group consisting ofdiethylenetriamine pentaacetic acid (DTPA), hydroxyethylethylenediaminetriacetic acid (HEDTA), triethylenetetraamine hexaacetic acid (TTHA),1,3-propanediamine tetraacetic acid (PDTA), 1,3-diamino-6-hydroxypropanetetraacetic acid (DPTA-OH), hydroxyethylimino diacetic acid (HIDA),dihydroxyethylglycine (DHEG), glycolether diamine tetraacetic acid(GEDTA), dicarboxymethyl glutamic acid (CMGA), (S,S)-ethylenediaminedisuccinic acid (EDDS), ethylenediamine tetraacetic acid (EDTA),nitrilotriacetic acid (NTA), and a salt thereof can be preferably used.

Furthermore, examples of the phenolic compound include compounds havingtwo or more phenolic hydroxyl groups, and phenolic compounds includingthe same as a basic skeleton. Examples of the former include catechol,gallic acid, pyrogallol, tannic acid, and the like. Meanwhile, examplesof the latter include flavonoids such as flavone, isoflavone, flavonol,flavanone, flavanol, anthocyanidin, aurone, chalcone, epigallocatechingallate, gallocatechin, theaflavin, daidzin, genistin, rutin, andmyricitrin, polyphenolic compounds including tannin, catechin and thelike, polyvinylphenol, water soluble resol, novolak resins, lignin, andthe like. Among them, tannin, gallic acid, catechin and pyrogallol areparticularly preferred.

As the sulfonic acid, at least one selected from the group consisting ofmethanesulfonic acid, isethionic acid, taurine, naphthalenedisulfonicacid, aminonaphthalenedisulfonic acid, sulfosalicylic acid, anaphthalenesulfonic acid-formaldehyde condensate,alkylnaphthalenesulfonic acid and the like, and a salt thereof can bepreferably used.

When sulfonic acid is used, coating performance and corrosion resistanceof the object following the chemical conversion treatment can beimproved. Although the mechanism is not clarified, the following groundsare conceived.

First, since there exist silica segregation products and the like on thesurface of the object such as steel plates to yield an un-uniformsurface composition, a portion not susceptible to etching in thechemical conversion treatment may be present. However, it is speculatedthat such a portion not susceptible to etching can be particularlyetched by adding sulfonic acid, and consequently, a uniform metal oxidefilm is likely to be formed on the object surface. In other words,sulfonic acid is believed to act as an etching accelerator.

Second, it is possible that in chemical conversion treatment, hydrogengas which can be generated by the chemical conversion reaction inhibitsthe reaction at the interface, and sulfonic acid is speculated to removethe hydrogen gas through a depolarizing action thereby accelerating thereaction.

Of these, use of taurine is preferred since it has both an amino groupand a sulfone group. The content of sulfonic acid is preferably in therange of 0.1 to 10,000 ppm, and more preferably in the range of 1 to1,000 ppm. When the content is less than 0.1 ppm, the effect is notsignificantly exhibited, while deposition of zirconium can be inhibitedwhen the content exceeds 10,000 ppm.

Use of ascorbic acid leads to uniform formation of the metal oxide filmsuch as zirconium oxide, tin oxide and the like on the object surface bythe chemical conversion treatment, and the coating performance andcorrosion resistance can be improved. Although the mechanism is notclarified, the etching action in the chemical conversion treatment isuniformly executed on the object such as steel plates, and consequently,it is speculated that zirconium oxide and/or tin oxide is deposited onthe etched part to form an entirely uniform metal oxide film. Inaddition, tin is speculated to become apt to be deposited in the form ofthe tin metal at the metal interface due to some influence, and as aconsequence, zirconium oxide is deposited at the part where the tinmetal deposited, whereby surface concealability on the object may beimproved as a whole. The content of ascorbic acid is preferably in therange of 5 to 5,000 ppm, and more preferably in the range of 20 to 200ppm. When the content is less than 5 ppm, the effect is notsignificantly exhibited, while deposition of zirconium can be inhibitedwhen the content exceeds 5,000 ppm.

When the chelating agent is included, its content is preferably 0.5 to10 times the concentration of the total concentration of other metalions except for zirconium such as tin ion and copper ion. When theconcentration is less than 0.5 times, the intended effect cannot beexhibited, while a concentration exceeding 10 times may adverselyinfluence on formation of the coating film.

The metal surface treatment liquid for cation electrodeposition coatingof the present invention can further contain a nitrogenous, sulfurand/or a phenolic rust-preventive agent. The rust-preventive agent caninhibit corrosion through forming an anti-corrosion coating film on themetal surface. As the nitrogenous, sulfurous, phenolic rust-preventiveagent, at least one selected from the group consisting of hydroquinone,ethyleneurea, quinolinol, thioures, benzotriazole and the like, and asalt thereof can be used. Use of the nitrogenous, sulfurous, phenolicrust-preventive agent in the metal surface treatment liquid for cationelectrodeposition coating of the present invention leads to uniformformation of the metal oxide film such as zirconium oxide, tin oxide andthe like on the object surface by the chemical conversion treatment,whereby the coating performance, corrosion resistance can be improved.Although the mechanism is not clarified, the followings are conceived.

That is, since there exist silica segregation products and the like onthe steel plate surface to yield an un-uniform surface composition, aportion having the conversion coating film formed by etching in thechemical conversion treatment, and a portion without formation of theconversion coating film due to different etching behavior thereby havingiron oxide may be present. The nitrogenous, sulfurous, phenolicrust-preventive agent improves primary rust-preventive propertiesthrough adsorbing to the portion without formation of the conversioncoating film in the chemical conversion treatment to cover the metalinterface. It is speculated that the coating performance, corrosionresistance of the object following the chemical conversion treatment canbe consequently improved.

In addition, when copper is excessively deposited on the conversioncoating film, this copper may serve as a cathode base point to form anelectrically un-uniform conversion coating film. However, by allowingthe rust-preventive agent to be adsorbed to the portion where anexcessive amount of copper deposited, improvement of the corrosionresistance is expected to be enabled by attaining a uniformelectrodeposition coating property on the object following the chemicalconversion treatment.

The content of the nitrogenous, sulfurous and/or phenolicrust-preventive agent is preferably in the range of 0.1 to 10,000 ppm,and more preferably in the range of 1 to 1,000 ppm. When the content isless than 0.1 ppm, the effect is not significantly exhibited, whiledeposition of zirconium can be inhibited when the content exceeds 10,000ppm.

The metal surface treatment liquid for cation electrodeposition coatingof the present invention may further contain aluminum ions and/or indiumions. Since these cations have similar functions to the tin ions, theycan be used in combination when the use of the tin ions alone cannotexhibit the effect. Of these, aluminum is more preferred. The content ofthe aluminum ions and/or the indium ions is preferably in the range of10 to 1,000 ppm, more preferably in the range of 50 to 500 ppm, andstill more preferably in the range of 100 to 300 ppm. The amount of thealuminum ions and indium ions can be a concentration accounting for, forexample, 2 to 1,000% of the zirconium ion concentration. Exemplary metalsurface treatment liquids for cation electrodeposition coating of thepresent invention include, for example, the metal surface treatmentliquids for cation electrodeposition coating which contain zirconiumions, tin ions and aluminum ions. These can further contain fluorine asdescribed later, and can also contain the polyamine compound describedlater.

The metal surface treatment liquid for cation electrodeposition coatingof the present invention may contain various cations in addition to theaforementioned components. Examples of the cation include magnesium,zinc, calcium, gallium, iron, manganese, nickel, cobalt, silver, and thelike. In addition, there exist cations and anions that are derived froma base or an acid added for adjusting the pH, or are included as thecounter ion of the aforementioned components.

The metal surface treatment liquid for cation electrodeposition coatingof the present invention can be produced by placing each of thecomponents thereof, and/or compound containing the same into water,followed by mixing.

Examples of the compound for supplying the zirconium ions includefluorozirconic acid, salts of fluorozirconic acid such as potassiumfluorozirconate and ammonium fluorozirconate, zirconium fluoride,zirconium oxide, zirconium oxide colloid, zirconyl nitrate, zirconiumcarbonate, and the like.

Examples of the compound that supplies the tin ions include tin sulfate,tin acetate, tin fluoride, tin chloride, tin nitrate, and the like. Onthe other hand, as the compound that supplies the fluorine ions, forexample, fluorides such as hydrofluoric acid, ammonium fluoride,fluoboric acid, ammonium hydrogen fluoride, sodium fluoride, sodiumhydrogen fluoride, and the like can be exemplified.

Additionally, a complex fluoride can also be used as the source, andexamples thereof include hexafluorosilicic acid salts, specifically,hydrofluosilicic acid, zinc hydrofluosilicicate, manganesehydrofluosilicate, magnesium hydrofluosilicate, nickelhydrofluosilicate, iron hydrofluosilicate, calcium hydrofluosilicate,and the like. Furthermore, a compound that supplies zirconium ions, andis a complex fluoride is also acceptable. Moreover, copper acetate,copper nitrate, copper sulfate, copper chloride and the like as thecompound that supplies copper ions; aluminum nitrate, aluminum fluorideand the like as the compound that supplies aluminum ions; and indiumnitrate, indium chloride and the like as the compound that suppliesindium ions can be exemplified, respectively.

After mixing these components, the metal surface treatment liquid forcation electrodeposition coating of the present invention can beregulated to have a predetermined value of pH using an acidic compoundsuch as nitric acid or sulfuric acid, and a basic compound such assodium hydroxide, potassium hydroxide or ammonia.

The metal surface treatment liquid for cation electrodeposition coatingof the present invention may contain an oxidizing agent. The oxidizingagent is particularly preferably at least one selected from the groupconsisting of nitric acid, nitrous acid, hydrogen peroxide, bromic acid,and salts of the same. The oxidizing agent allows a metal oxide film tobe uniformly formed on the surface of an object, whereby coatability andcorrosion resistance of the object can be improved.

Although the mechanism is not clarified, it is speculated that use ofthe oxidizing agent in a specified amount allows the etching action inthe chemical conversion treatment to be uniformly executed on an objectsuch as a steel plate, whereby zirconium oxide and/or tin oxide isdeposited at the etched part to form an entirely uniform metal oxidefilm. It is also speculated that the oxidizing agent in the specifiedamount renders tin readily deposited as a tin metal at the metalinterface, and thus zirconium oxide is deposited at the portions ofdeposition of the tin metal, whereby the surface concealability on theentire object is improved.

In order to affect such an action, the content of each oxidizing agentis as in the following. Accordingly, the content of nitric acid ispreferably in the range of 100 to 100,000 ppm, more preferably in therange of 1,000 to 20,000 ppm, and still more preferably in the range of2,000 to 10,000 ppm. The content of nitrous acid and bromic acid ispreferably in the range of 5 to 5,000 ppm, and more preferably in therange of 20 to 200 ppm. The content of nitrous acid and bromic acid ispreferably in the range of 5 to 5,000 ppm, and more preferably in therange of 20 to 200 ppm. The content of hydrogen peroxide is preferablyin the range of 1 to 1,000 ppm, and more preferably in the range of 5 to100 ppm. When content of each is less than the lower limit, theaforementioned effect is not significantly exhibited, while thedeposition of zirconium can be inhibited when the content exceeds theupper limit.

The method of the metal surface treatment of the present inventionincludes a step of subjecting a metal base material to a surfacetreatment using the metal surface treatment liquid described above.

The metal base material is not particularly limited as long as it can becation electrodeposited, and for example, an iron-based metal basematerial, aluminum-based metal base material, zinc-based metal basematerial and the like can be exemplified.

Examples of the iron-based metal base material include cold-rolled steelplates, hot-rolled steel plates, soft steel plates, high-tensile steelplates, and the like. Moreover, examples of the aluminum-based metalbase material include 5,000 series aluminum alloys, 6,000 seriesaluminum alloys, and aluminum-coated steel plates treated byaluminum-based electroplating, hot dipping, or vapor deposition plating.Furthermore, examples of the zinc-based metal base material include zincor zinc-based alloy coated steel plates treated by zinc-basedelectroplating, hot dipping, or vapor deposition plating such as zinccoated steel plate, zinc-nickel coated steel plate, zinc-titanium coatedsteel plate, zinc-magnesium coated steel plate, zinc-manganese coatedsteel plate, and the like. There are a variety of grades of thehigh-tensile steel plate depending on the strength and manufacturemethod, and examples thereof include JSC400J, JSC440P, JSC440W, JSC590R,JSC590T, JSC590Y, JSC780T, JSC780Y, JSC980Y, JSC1180Y, and the like.

Metal base materials including a combination of multiple kinds of metalssuch as iron-based, aluminum-based, zinc-based metals and the like(including joint area and contact area of different kinds of metals) canbe simultaneously applied as the metal base material.

The surface treatment step may be carried out by bringing the metalsurface treatment liquid into contact with the metal base material.Specific examples of the method include a dipping method, a sprayingmethod, a roll coating method, a pouring method, and the like.

The treatment temperature in the surface treatment step preferably fallswithin the range of 20 to 70° C. When the temperature is lower than 20°C., it is possible to cause failure in formation of a sufficient coatingfilm, while a corresponding effect cannot be expected at a temperatureabove 70° C. The lower limit and the upper limit are more preferably 30°C. and 50° C., respectively.

The treatment time period in the surface treatment step is preferably 2to 1100 seconds. When the time period is less than 2 seconds, asufficient coating film amount may not be attained, while acorresponding effect cannot be expected even though it is longer than1100 seconds. The lower limit and the upper limit are still morepreferably 30 seconds and 120 seconds, respectively. Accordingly, acoating film is formed on the metal base material.

The surface treated metal base material of the present invention isobtained by the surface treatment method described above. On the surfaceof the metal base material is formed a coating film that containszirconium and tin. The element ratio of zirconium/tin in the coatingfilm is preferably in the range of 1/10 to 10/1 on a mass basis. Whenthe ratio is out of this range, the intended performance may not beattained.

The content of zirconium in the coating film is preferably no less than10 mg/m² in the case of iron-based metal base materials. When thecontent is less than 10 mg/m², sufficient anti-corrosion properties maynot be achieved. The content is more preferably no less than 20 mg/m²,and still more preferably no less than 30 mg/m². Although the upperlimit is not specifically defined, too large an amount of the coatingfilm may lead to an increased likelihood of crack generation of therust-preventive coating film, and may make it difficult to obtain auniform coating film. In this respect, the content of zirconium in thecoating film is preferably no greater than 1 g/m², and more preferablyno greater than 800 mg/m².

When the coating film is formed using the metal surface treatment liquidwhich contains copper ions, the content of copper in the coating film ispreferably no less than 0.5 mg/m² in order to achieve the intendedeffect.

The method of cation electrodeposition coating of the present inventionincludes a step of subjecting a metal base material to a surfacetreatment using the metal surface treatment liquid described above, anda step of subjecting the surface treated metal base material to cationelectrodeposition coating.

The surface treatment step in the aforementioned cationelectrodeposition coating is same as the surface treatment step in thesurface treatment method described above. The surface treated metal basematerial obtained in the surface treatment step may be subjected to thecation electrodeposition coating step directly or after washing.

In the cation electrodeposition coating step, the surface treated metalbase material is subjected to the cation electrodeposition coating. Inthe cation electrodeposition coating, the surface treated metal basematerial is dipped in cation electrodeposition coating solution, and avoltage of 50 to 450 V is applied thereto using the same as a cathodefor a certain period of time. Although the application time period ofvoltage may vary depending on the conditions of the electrodeposition,it is generally 2 to 4 minutes.

As the cation electrodeposition coating solution, a generally well knownone can be used. Specifically, such general coating solutions areprepared by blending: a binder cationized through adding amine orsulfide to an epoxy group carried by an epoxy resin or an acrylic resin,followed by adding thereto a neutralizing acid such as acetic acid;block isocyanate as a curing agent; and a pigment dispersing pasteincluding a rust-preventive pigment dispersed in a resin.

After completing the cation electrodeposition coating step, a hardenedcoated film can be obtained by baking at a predetermined temperaturedirectly, or after washing with water. Although the baking conditionsmay vary depending on the type of the cation electrodeposition coatingsolution used, usually the baking may be conducted in the range of 120to 260° C., and preferably in the range of 140 to 220° C. The bakingtime period can be 10 to 30 minutes. The resulting metal base materialcoated by the cation electrodeposition is also involved as an aspect ofthe present invention.

EXAMPLES Production Example 1 Production of Hydrolysis Condensate ofAminosilane, Part 1

As aminosilane, 5 parts by mass of KBE603(3-aminopropyl-triethoxysilane, effective concentration: 100%,manufactured by Shin-Etsu Chemical Co., Ltd.) was added dropwise using adropping funnel to a mixed solvent (solvent temperature: 25° C.)containing 47.5 parts by mass of deionized water and 47.5 parts by massof isopropyl alcohol over 60 minutes to a homogenous state, followed byallowing for reaction under a nitrogen atmosphere at 25° C. for 24hours. Then, the reaction solution was subjected to a reduced pressureto allow for evaporation of isopropyl alcohol, and deionized water wasfurther added thereto, whereby a hydrolysis condensate of aminosilaneincluding 5% of the active ingredient was obtained.

Production Example 2 Production of Hydrolysis Condensate of Aminosilane,Part 2

In a similar manner to Production Example 1, except that the amountswere changed to 20 parts by mass of KBE603, 40 parts by mass ofdeionized water, and 40 parts by mass of isopropyl alcohol, a hydrolysiscondensate of aminosilane including 20% of the active ingredient wasobtained.

Example 1

A metal surface treatment liquid for cation electrodeposition coatingwas obtained by: mixing a 40% aqueous zircon acid solution as azirconium ion source, tin sulfate as a tin ion source, and hydrofluoricacid; diluting the mixture so as to give a zirconium ion concentrationof 500 ppm, and a tin ion concentration of 30 ppm; and adjusting the pHto 3.5 using nitric acid and sodium hydroxide. Measurement of freefluorine ion concentration using a fluorine ion meter after adjustingthe pH of this treatment liquid to 3.0 revealed a value of 5 ppm.

Example 2

A metal surface treatment liquid for cation electrodeposition coatingwas obtained in a similar manner to Example 1 except that: thehydrolysis condensate of aminosilane obtained in Production Example 1was further added to be 200 ppm; tin sulfate was changed to tin acetateso as to give the tin ion concentration of 10 ppm; and the pH wasadjusted to 2.75. Measurement of the free fluorine ion concentrationusing a fluorine ion meter after adjusting the pH of this treatmentliquid to 3.0 revealed a value of 5 ppm.

Example 3

A metal surface treatment liquid for cation electrodeposition coatingwas obtained in a similar manner to Example 1 except that:polyallylamine “PAA-H-10C” (trade name, manufactured by Nitto BosekiCo., Ltd.) was further added to be 25 ppm; zirconium ion concentrationwas changed to 250 ppm; and the pH was adjusted to 3.0. Measurement ofthe free fluorine ion concentration using a fluorine ion meter on thistreatment liquid revealed a value of 5 ppm.

Example 4

A metal surface treatment liquid for cation electrodeposition coatingwas obtained in a similar manner to Example 1, except that: coppernitrate was further added so as to give a copper ion concentration of 10ppm; the tin ion concentration was changed to 10 ppm; and the pH wasadjusted to 3.0. Measurement of the free fluorine ion concentrationusing a fluorine ion meter on this treatment liquid revealed a value of5 ppm.

Example 5

A metal surface treatment liquid for cation electrodeposition coatingwas obtained in a similar manner to Example 4, except that: thehydrolysis condensate of aminosilane obtained in Production Example 2was further added to be 200 ppm; and the tin ion concentration waschanged to 30 ppm. Measurement of the free fluorine ion concentrationusing a fluorine ion meter on this treatment liquid revealed a value of5 ppm.

Example 6

A metal surface treatment liquid for cation electrodeposition coatingwas obtained in a similar manner to Example 2, except that: aluminumnitrate was further added so as to give an aluminum ion concentration of200 ppm; and tin sulfate was changed to tin acetate so as to give thetin ion concentration of 30 ppm. Measurement of the free fluorine ionconcentration using a fluorine ion meter after adjusting the pH of thistreatment liquid to 3.0 revealed a value of 5 ppm.

Examples 7 and 8

Metal surface treatment liquids for cation electrodeposition coatingwere obtained in a similar manner to Example 6, except that the pH wasadjusted to 3.5 and 4.0. The free fluorine ion concentration measuredusing a fluorine ion meter after adjusting the pH of this treatmentliquid to 3.0 is shown in Table 1.

Examples 9 to 16

Metal surface treatment liquids for cation electrodeposition coatingwere obtained in a similar manner to Example 7, except that the amountof added 40% aqueous zirconic acid solution, tin sulfate, and aluminumnitrate was changed so as to give a zirconium ion concentration, a tinion concentration, and an aluminum ion concentration as shown inTable 1. The free fluorine ion concentration measured using a fluorineion meter after adjusting the pH of this treatment liquid to 3.0 isshown in Table 1.

Example 17

A metal surface treatment liquid for cation electrodeposition coatingwas obtained in a similar manner to Example 2, except that: indiumnitrate was further added so as to give an indium ion concentration of200 ppm; tin sulfate was changed to tin fluoride so as to give a tin ionconcentration of 30 ppm; and the pH was adjusted to 3.5. Measurement ofthe free fluorine ion concentration using a fluorine ion meter afteradjusting the pH of this treatment liquid to 3.0 revealed a value of 5ppm.

Example 18

A metal surface treatment liquid for cation electrodeposition coatingwas obtained in a similar manner to Example 2, except that:diethylenetriamine pentaacetic acid (DTPA) was further added as achelating agent to give a concentration of 100 ppm; tin acetate waschanged to tin sulfate, thereby changing the tin ion concentration to 30ppm; and further, the zirconium ion concentration was changed to 1,000ppm. Measurement of the free fluorine ion concentration using a fluorineion meter after adjusting the pH of this treatment liquid to 3.0revealed a value of 10 ppm.

Example 19

A metal surface treatment liquid for cation electrodeposition coatingwas obtained in a similar manner to Example 2, except that: sodiumnitrate was further added so as to give a sodium ion concentration of5,000 ppm; and the tin ion concentration was changed to 30 ppm.Measurement of the free fluorine ion concentration using a fluorine ionmeter after adjusting the pH of this treatment liquid to) 3.0 revealed avalue of 5 ppm.

Example 20

A metal surface treatment liquid for cation electrodeposition coatingwas obtained in a similar manner to Example 5, except that: glycine aschelating agents and copper nitrate further added so as to give aconcentration of 50 ppm and copper ion concentration of 10 ppm,respectively; and the concentration of polyamine was changed to 100 ppm.Measurement of the free fluorine ion concentration using a fluorine ionmeter on this treatment liquid revealed a value of 5 ppm.

Examples 21 to 31

Metal surface treatment liquids for cation electrodeposition coatingwere respectively obtained in a similar manner to Example 1, exceptthat: polyamine as described in Table 1 was added in a specified amount;and the concentration of the other component was changed as shown inTable 1. The free fluorine ion concentrations measured using a fluorineion meter on these treatment liquids under a condition of pH 3.0 areshown together in Table 1.

Examples 32 to 50

Metal surface treatment liquids for cation electrodeposition coatingwere respectively obtained in a similar manner to Example 1, exceptthat: sulfonic acid described in Table 2 was added in a specifiedamount; and polyamine and the other component were changed as shown inTable 2. The free fluorine ion concentrations measured using a fluorineion meter on these treatment liquids under a condition of pH 3.0 areshown together in Table 2. In Table 2, the used naphthalenesulfonicacid-formaldehyde condensate was DEMOL NL manufactured by KaoCorporation; sodium alkylnaphthalenesulfonate was PELEX NBL manufacturedby Kao Corporation; and sodium polystyrenesulfonate was P-NASS-1manufactured by Tosoh Corporation.

Examples 51

Metal surface treatment liquids for cation electrodeposition coatingwere respectively obtained in a similar manner to Example 1, exceptthat: ascorbic acid as described in Table 3 was added in a specifiedamount; and polyamine and the other component were changed as shown inTable 3. The free fluorine ion concentrations measured using a fluorineion meter on these treatment liquids under a condition of pH 3.0 areshown together in Table 3.

Examples 52 to 59

Metal surface treatment liquids for cation electrodeposition coatingwere respectively obtained in a similar manner to Example 1, exceptthat: the oxidizing agent described in Table 3 was added in a specifiedamount; and polyamine and the other component were changed as shown inTable 3. The free fluorine ion concentrations measured using a fluorineion meter on these treatment liquids under a condition of pH 3.0 areshown together in Table 3.

Examples 60 to 74

Metal surface treatment liquids for cation electrodeposition coatingwere respectively obtained in a similar manner to Example 1, exceptthat: the nitrogen-based rust-preventive agent, the sulfur-basedrust-preventive agent, or the phenol-based rust-preventive agentdescribed in Table 3 was added in a specified amount; and polyamine andthe other component were changed as shown in Table 3. The free fluorineion concentrations measured using a fluorine ion meter on thesetreatment liquids under a condition of pH 3.0 are shown together inTable 3.

Examples 75 to 77

Metal surface treatment liquids for cation electrodeposition coatingwere respectively obtained in a similar manner to Example 1, exceptthat: instead of a cold-rolled steel plate (SPC) a high-tensile steelplate was used as the base plate that is the object; and polyamine andthe other component described in Table 3 were changed as shown in Table3. The free fluorine ion concentrations measured using a fluorine ionmeter on these treatment liquids under a condition of pH 3.0 are showntogether in Table 3.

Examples 78 to 106

With respect to Examples 2, 3, and 5 to 31, metal surface treatmentliquids for cation electrodeposition coating were obtained in a similarmanner to each Example, except that polyamine was not added. The freefluorine ion concentrations measured using a fluorine ion meter afteradjusting the pH of the treatment liquids to 3.0 are shown in Table 4.

Comparative Examples 1 to 6 Preparation of Comparative Metal SurfaceTreatment Liquid

According to the description in Table 1 and Table 3, comparative metalsurface treatment liquids were obtained, respectively, based on theaforementioned Examples. Thus resulting metal surface treatment liquidsare summarized in Table 1 and Table 3.

TABLE 1 Added Component Zr Tin ion Sn (Concentraion in Parenthesis(ppm)) Free Fluorine Concentration supplying Concentration Sn/ZrPolyamine ion (ppm) compound (ppm) ratio pH Compound OthersConcentration Example 1 500 tin sulfate 30 0.06 3.5 absent 5 Example 2500 tin sulfate 10 0.02 2.75 Production 5 Exapmle 1 (200) Example 3 250tin sulfate 30 0.12 3 poly 5 allylamine (25) Example 4 500 tin sulfate10 0.02 3 absent copper nitrate (10) 5 Example 5 500 tin sulfate 30 0.063 Production copper nitrate (10) 5 Exapmle 2 (200) Example 6 500 tinacetate 30 0.06 2.75 Production aluminum nitrate (200) 5 Exapmle 1 (200)Example 7 500 tin acetate 30 0.06 3.5 Production aluminum nitrate (200)5 Exapmle 1 (200) aluminum nitrate (200) 5 Example 8 500 tin acetate 300.06 4 Production aluminum nitrate (200) 7 Exapmle 1 (200) Example 91000 tin acetate 30 0.03 3.5 Production aluminum nitrate (200) 7 Exapmle1 (200) Example 10 500 tin acetate 30 0.06 3.5 Production aluminumnitrate (500) 5 Exapmle 1 (200) Example 11 500 tin acetate 30 0.06 3.5Production aluminum 5 Exapmle 1 (200) nitrate (1000) Example 12 500 tinacetate 10 0.02 3.5 Production aluminum nitrate (500) 5 Exapmle 1 (200)Example 13 500 tin acetate 200 0.4 3.5 Production aluminum nitrate (500)5 Exapmle 1 (200) Example 14 200 tin acetate 10 0.05 3.5 Productionaluminum nitrate (200) 7 Exapmle 1 (200) Example 15 200 tin acetate 300.15 3.5 Production aluminum nitrate (200) 5 Exapmle 1 (200) Example 16200 tin acetate 70 0.35 3.5 Production aluminum nitrate (200) 5 Exapmle1 (200) Example 17 500 tin 30 0.06 3.5 Production indium nitrate (50) 5fluoride Exapmle 1 (200) Example 18 1000 tin sulfate 30 0.03 2.75Production DTPA (100) 10 Exapmle 1 (200) Example 19 500 tin sulfate 300.06 2.75 Production sodium nitrate (5000) 5 Exapmle 1 (200) Example 20500 tin sulfate 30 0.06 3 Production coppoer sulfate (10), 5 Exapmle 2(100) glycine (50) Example 21 20 tin sulfate 5 0.25 3 Production Exapmle2 1 (10) Example 22 500 tin sulfate 20 0.04 2 Production Exapmle 1 1(200) Example 23 500 tin sulfate 30 0.06 5.5 Production Exapmle 20 1(200) Example 24 5000 tin sulfate 25 0.005 3 Production Exapmle 10 1(2000) Example 25 50 tin sulfate 10 0.2 3 Production Exapmle 3 2 (50)Example 26 50 tin sulfate 50 1 3 Production Exapmle 1 2 (25) Example 27500 tin sulfate 30 0.06 3 Production Exapmle 0 1 (50) Example 28 500 tinsulfate 30 0.06 2.75 Production Exapmle 0.1 2 (50) Example 29 500 tinsulfate 30 0.06 2.75 Production Exapmle 0.6 2 (50) Example 30 500 tinsulfate 30 0.06 4 Production Exapmle 20 1 (200) Example 31 500 tinsulfate 30 0.06 4.5 Production Exapmle 50 1 (200) Comparative 500 absent0 0 3.5 Production Exapmle 7 Example 1 1 (200) Comparative 500 absent 00 3 Production Exapmle aluminum nitrate (500) 5 Example 2 1 (200)Comparative 50 absent 0 0 3.5 Production Exapmle 5 Example 3 1 (200)Comparative 500 tin sulfate 250 0.5 1 Production Exapmle 5 Example 4 1(200) Comparative 500 tin sulfate 250 0.5 8 Production Exapmle 5 Example5 1 (200)

TABLE 2 Added Component Zr Tin ion Sn (Concentraion in Parenthesis(ppm)) Concentration supplying Concentration Polyamine Free Fluorine ion(ppm) compounds (ppm) Sn/Zr ratio pH Compound Other Metal OthersConcentration Example 500 tin sulfate 30 0.06 3.5 Production taurine(100) 5 32 Exapmple 1 (200) Example 500 tin sulfate 30 0.06 3.5Production methan sulfonic 5 33 Exapmple acid (100) 1 (200) Example 500tin sulfate 30 0.06 3.5 Production isethionic 5 34 Exapmple acid (100) 1(200) Example 500 tin sulfate 30 0.06 3.5 Production sodium 5 35Exapmple naphthalenedisulfonate 1 (200) (100) Example 500 tin sulfate 300.06 3.5 Production sodium 5 36 Exapmple aminonaphthalene 1 (200)disulfonate (100) Example 500 tin sulfate 30 0.06 3.5 Productionsulfosalicylic 5 37 Exapmple acid (100) 1 (200) Example 500 tin sulfate30 0.06 3.5 Production naphthalene 5 38 Exapmple sulfonic acid- 1 (200)formaldehyde condensate (100) Example 500 tin sulfate 30 0.06 3.5Production sodium 5 39 Exapmple alkylnaphthalene 1 (200) sulfonate (100)Example 500 tin sulfate 30 0.06 3.5 Production copper taurine (100) 5 40Exapmple nitrate (10) 1 (200) Example 500 tin sulfate 30 0.06 3.5 —copper taurine (100) 5 41 nitrate (10) Example 500 tin sulfate 30 0.063.5 — aluminum methan sulfonic 5 42 nitrate (200) acid (100) Example 500tin sulfate 30 0.06 3.5 — copper isethionic 5 43 nitrate (10) acid (100)Example 500 tin sulfate 30 0.06 3.5 — aluminum sodium 5 44 nitratenaphthalenedisulfonate (200) (100) Example 500 tin sulfate 30 0.06 3.5 —copper sodium 5 45 nitrate (10) aminonaphthalene disulfonate (100)Example 500 tin sulfate 30 0.06 3.5 — aluminum sulfosalicylic 5 46nitrate acid (100) (200) Example 500 tin sulfate 30 0.06 3.5 — coppernaphthalene 5 47 nitrate (10) sulfonic acid- formaldehyde condensate(100) Example 500 tin sulfate 30 0.06 3.5 — aluminum sodium 5 48 nitratealkylnaphthalene (200) sulfonate (100) Example 500 tin sulfate 30 0.063.5 — copper sodium 5 49 nitrate (10) styrenesulfonate (100) Example 500tin sulfate 30 0.06 3.5 — aluminum sodium 5 50 nitrate polystyrene (200)sulfonate (100)

TABLE 3 Added Component (Concentration in Zr Tin ion Sn Parenthesis(ppm)) Concentration Supplying Concentration Polyamine Other FreeFluorine ion (ppm) Compounds (ppm) Sn/Zr ratio pH Compounds Metal OthersConcentration Example 51 500 tin 30 0.06 3.5 Production — sodium 5sulfate Example ascorbate 1 (200) (50) Example 52 500 tin 30 0.06 3.5Production — as sodium 5 sulfate Example nitrate 1 (200) (10000) Example53 500 tin 30 0.06 3.5 Production — hydrogen 5 sulfate Example peroxide(10) 1 (200) Example 54 500 tin 30 0.06 3.5 Production — sodium 5sulfate Example nitrite (50) 1 (200) Example 55 500 tin 30 0.06 3.5Production — sodium 5 sulfate Example bromate (100) 1 (200) Example 56500 tin 30 0.06 3.5 — copper as sodium 5 sulfate nitrate (10) nitrate(10000) Example 57 500 tin 30 0.06 3.5 — aluminum hydrogen 5 sulfatenitrate peroxide (10) (200) Example 58 500 tin 30 0.06 3.5 — coppersodium 5 sulfate nitrate (10) nitrite (50) Example 59 500 tin 30 0.063.5 — aluminum sodium 5 sulfate nitrate bromate (100) (200) Example 60500 tin 30 0.06 3.5 Production — hydroquinone 5 sulfate Example (100) 1(200) Example 61 500 tin 30 0.06 3.5 Production — ethylene 5 sulfateExample urea (100) 1 (200) Example 62 500 tin 30 0.06 3.5 Production —quinolinol (100) 5 sulfate Example 1 (200) Example 63 500 tin 30 0.063.5 Production — thiourea (100) 5 sulfate Example 1 (200) Example 64 500tin 30 0.06 3.5 Production — benzotriazole 5 sulfate Example (100) 1(200) Example 65 500 tin 30 0.06 3.5 Production — mercaptobenzothiazole5 sulfate Example (100) 1 (200) Example 66 500 tin 30 0.06 3.5Production — KBM803 (100) 5 sulfate Example 1 (200) Example 67 500 tin30 0.06 3.5 Production copper benzotriazole 5 sulfate Example nitrate(10) (100) 1 (200) Example 68 500 tin 30 0.06 3.5 — copper hydroquinone5 sulfate nitrate (10) (100) Example 69 500 tin sulfate 30 0.06 3.5 —copper ethylene urea (100) 5 nitrate (10) Example 70 500 tin sulfate 300.06 3.5 — copper quinolinol (100) 5 nitrate (10) Example 71 500 tinsulfate 30 0.06 3.5 — copper thiourea (100) 5 nitrate (10) Example 72500 tin sulfate 30 0.06 3.5 — copper benzotriazole (100) 5 nitrate (10)Example 73 500 tin sulfate 30 0.06 3.5 — copper mercaptobenzothiazole 5nitrate (10) (100) Example 74 500 tin sulfate 30 0.06 3.5 — copperKBM803 (100) 5 nitrate (10) Example 75 500 tin sulfate 30 0.06 3.5Production copper as sodium nitrate 5 Example nitrate (10) (10000) 1(200) Example 76 500 tin sulfate 30 0.06 3.5 Production copper taurine(100) 5 Example nitrate (10) 1 (200) Example 77 500 tin sulfate 30 0.063.5 Production copper benzotriazole (100) 5 Example nitrate (10) 1 (200)Comparative 500 — — — 3.5 Production — 5 Example 6 Example 1 (200)

TABLE 4 Added Component (Concentration in Zr Tin ion Sn Parenthesis(ppm)) Free Fluorine Concentration Supplying Concentration Sn/ZrPolyamine ion (ppm) Compounds (ppm) ratio pH Compounds OthersConcentration Example 78 500 tin sulfate 10 0.02 2.75 — 5 Example 79 250tin sulfate 30 0.12 3 — 5 Example 80 500 tin sulfate 30 0.06 3 — copper5 nitrate (10) Example 81 500 tin sulfate 30 0.06 2.75 — aluminum 5nitarte (200) Example 82 500 tin acetate 30 0.06 3.5 — aluminum 5nitarte (200) Example 83 500 tin acetate 30 0.06 4 — aluminum 5 nitarte(200) Example 84 1000 tin acetate 30 0.03 3.5 — aluminum 7 nitarte (200)Example 85 500 tin acetate 30 0.06 3.5 — aluminum 5 nitrate (500)Example 86 500 tin acetate 30 0.06 3.5 — aluminum 5 nitrate (1000)Example 87 500 tin acetate 10 0.02 3.5 — aluminum 5 nitrate (500)Example 88 500 tin acetate 200 0.4 3.5 — aluminum 5 nitrate (500)Example 89 200 tin acetate 10 0.05 3.5 — aluminum 7 nitarte (200)Example 90 200 tin acetate 30 0.15 3.5 — aluminum 5 nitarte (200)Example 91 200 tin acetate 70 0.35 3.5 — aluminum 5 nitarte (200)Example 92 500 tin fluoride 30 0.06 3.5 — indium 5 nitrate (50) Example93 1000 tin sulfate 30 0.03 2.75 — DTPA (100) 10 Example 94 500 tinsulfate 30 0.06 2.75 — sodium 5 nitrate (5000) Example 95 500 tinsulfate 30 0.06 3 — copper 5 nitrate (10), glycine (50) Example 96 20tin sulfate 5 0.25 3 — 2 Example 97 500 tin sulfate 20 0.04 2 — 1Example 98 500 tin sulfate 30 0.06 5.5 — 20 Example 99 5000 tin sulfate25 0.005 3 — 10 Example 50 tin sulfate 10 0.2 3 — 3 100 Example 50 tinsulfate 50 1 3 — 1 101 Example 500 tin sulfate 30 0.06 3 — 0 102 Example500 tin sulfate 30 0.06 2.75 — 0.1 103 Example 500 tin sulfate 30 0.062.75 — 0.6 104 Example 500 tin sulfate 30 0.06 4 — 20 105 Example 500tin sulfate 30 0.06 4.5 — 50 106

Surface Treatment

As metal base materials, a commercially available cold-rolled steelplate (SPC, manufactured by Nippon Testpanel Co., Ltd., 70 mm×150 mm×0.8mm) was provided for Examples 1 to 74, Examples 78 to 106, andComparative Examples 1 to 5, and a high-tensile steel plate (70 mm×150mm×1.0 mm) was provided for Examples 75 to 77, and Comparative Example6. These plates were subjected to a degreasing treatment using“SURFCLEANER EC92” (trade name, manufactured by Nippon Paint Co., Ltd.)as an alkali degreasing treatment agent at 40° C. for 2 minutes. Thisplate was dipped and washed in a water washing bath, and then washed byspraying tap water thereon for approximately 30 seconds.

The metal base material following the degreasing treatment was subjectedto a surface treatment by dipping thereof in the metal surface treatmentliquid prepared in Examples and Comparative Examples at 40° C. for 90seconds. However, the treatment time period was 240 seconds and 15seconds, respectively, in Examples 21 and 22. After completing thesurface treatment, the plate was dried at 40° C. for 5 minutes, and thethus surface treated metal base material was obtained. Unlessspecifically stated, this surface treated metal base material was usedas a test plate in the following evaluation.

Measurement of Element Content in Coating Film

The content of each element included in the coating film was measuredusing an X-ray fluorescence spectrometer “XRF1700” manufactured byShimadzu Corporation.

Primary Rust Prevention

After immersing the test plate in pure water at 25° C. for 5 hours, thegeneration state of rust was visually observed.

A: no rust generation observedB: slightly generated rust observedC: rust generation clearly identified

Observation of Sludge

With 10 L of the surface treatment liquids of the Examples andComparative Examples, 200 test panels were subjected to the surfacetreatment and evaluation was made according to the following standardsthrough visual observation as to whether the surface treatment liquidbecame turbid due to generation of sludge following the lapse of 30 daysat room temperature.

A: transparent liquidB: slightly turbidC: turbidD: precipitate (sludge) generated

Evaluation of Throwing Power

The throwing power was evaluated according to a “four-plate box method”described in Japanese Unexamined Patent Application, First PublicationNo. 2000-038525. More specifically, as shown in FIG. 1, test plates 1 to4 were arranged to stand up in parallel with intervals of 20 mm toproduce a box 10 sealed with an insulator such as cloth adhesive tape atthe underneath of both side faces and the bottom face. Through-holes 5having a diameter of 8 mm were provided underneath the metal materials1, 2 and 3, except for metal material 4.

This box 10 was dipped into an electrodeposition coating vessel 20filled with a cation electrodeposition coating solution “POWERNICS 110”(trade name, manufactured by Nippon Paint Co., Ltd.). In this case, thecation electrodeposition coating solution entered inside the box 10 onlyfrom each through-hole 5.

Each of the test plates 1 to 4 was electrically connected while stirringthe cation electrodeposition coating solution with a magnetic stirrer,and a counter electrode 21 was arranged such that the distance from thetest plate 1 became 150 mm. Voltage was applied with each of the testplates 1 to 4 as cathodes, and the counter electrode 21 as an anode toexecute cation electrodeposition coating. The coating was carried out byelevating to the intended voltage (210 V and 160 V) over 30 seconds frominitiation of the application, and thereafter maintaining the voltagefor 150 seconds. The bath temperature in this process was regulated to30° C.

After washing each of the test plates 1 to 4 with water after coating,they were baked at 170° C. for 25 minutes, followed by air cooling. Thethrowing power was then evaluated by measuring the film thickness of thecoated film formed on side A of the test plate 1 that is the closest tothe counter electrode 21, and the film thickness of the coated filmformed on side G of the test plate 4 that is the farthest from thecounter electrode 21 to determine a ratio of the film thickness (sideG)/film thickness (side A). As this value becomes greater, betterevaluation of the throwing power can be decided. The acceptable levelwas no less than 40%.

Coating Voltage

Using the surface treatment liquids of Examples and ComparativeExamples, cold-rolled steel plates and zinc coated steel plates weresubjected to a surface treatment, whereby test plates were obtained.Using the cation electrodeposition coating solution “POWERNICS 110”described above on these test plates, the voltage required for obtaininga 20 μm electrodeposition coated film was determined. The difference incoating voltage required for obtaining the 20 μm electrodepositioncoated film was then determined between the case in which the metal basematerial was a zinc coated steel plate, and the case of the cold-rolledsteel plate. As the difference becomes smaller, superiority as a surfacetreated coating film is suggested. A difference of no greater than 40 Vis acceptable.

The voltage required for obtaining a 20 μm electrodeposition coated filmwas determined as in the following manner. Under the electrodepositioncondition, the voltage was elevated to a specified voltage over 30seconds, and thereafter maintaining for 150 seconds. The resulting filmthickness was measured. Such a procedure was conducted for 150 V, 200 V,and 250 V. Thus, a voltage to give a 20 μm film thickness was derivedfrom the formula of relationship between the determined voltage and thefilm thickness.

Appearance of Coating

The test plate was subjected to cation electrodeposition coating, andthe appearance of the resulting electrodeposition coated film wasevaluated according to the following standards. The results are shown inTables 5 to 8.

A: uniform coated film obtainedB: nearly uniform coated film obtainedC: some non-uniformity of the coated film foundD: non-uniformity of the coated film found

Secondary Adhesion Test (SDT)

After forming a 20 μm electrodeposition coated film, the test plateswere incised to provide two parallel cut lines that ran longitudinally,with the depth to reach to the metal basis material, and then immersedin a 5% aqueous sodium chloride solution at 55° C. for 240 hours. Afterwater washing and air drying, an adhesive tape “L-PACK LP-24” (tradename, manufactured by Nichiban Co., Ltd.) was adhered to the portionincluding the cuts. Then, the adhesive tape was peeled off abruptly. Themaximum width (one side) of the coating adhered to the stripped adhesivetape was measured.

A: 0 mm

B: less than 2 mmC: at least 2 mm to less than 5 mmD: no less than 5 mm

Cycle Corrosion Test (CCT)

After forming the 20 μm electrodeposition coated film on the test plate,the edge and back face was sealed with a tape, thereby providing crosscuttings that reached to the metal basis material. A 5% aqueous sodiumchloride solution incubated at 35° C. was continuously sprayed for 2hours onto this sample in a salt spray tester kept at 35° C., and with ahumidity of 95%. Subsequently, it was dried under conditions of 60° C.and with a humidity of 20 to 30% for 4 hours. Such a sequence ofprocedures repeated three times in 24 hours was defined as one cycle,and 200 cycles were carried out. Thereafter, the width of the swellingportion of the coated film (both sides) was measured.

A: less than 6 mmB: at least 6 mm to less than 8 mmC: at least 8 mm to less than 10 mmD: no less than 10 mm

Salt Spray Test (SST)

After forming the 20 μm electrodeposition coated film on the test plate,the edge and the back face were sealed with a tape, thereby providingcross cuttings that reached to the metal basis material. A 5% aqueoussodium chloride solution incubated at 35° C. was continuously sprayedfor 840 hours to this sample in a salt spray tester kept at 35° C., andwith a humidity of 95%. After washing with water and air drying, anadhesive tape “L-PACK LP-24” (trade name, manufactured by Nichiban Co.,Ltd.) was adhered on the portion including the cuts. Then, the adhesivetape was peeled off quickly. The maximum width (one side) of the coatingadhered to the stripped adhesive tape was measured.

A: less than 2 mmB: at least 2 mm to less than 5 mmC: no less than 5 mm

The evaluation results are summarized in Tables 5 to 8.

TABLE 5 Content Primary Throwing Difference Appearance of Element RustObservation Power (%) in Coating of Zr Si Sn Cu Prevention of sludge 210V 160 V Voltage (V) Coating SDT CCT SST Example 1 45 22 A B 60% 52% 30 A— B A Example 2 51 3.3 13 A B 57% 25% 40 B A B A Example 3 44 24 A B 57%44% 40 A B B A Example 4 55 16 8 A B 58% 51% 40 A A A A Example 5 46 6.227 11  A B 61% 55% 20 A A A A Example 6 42 3.5 19 A B 57% 47% 40 A A B AExample 7 56 3.7 15 — A B 53% 42% 30 B A B A Example 8 62 4.1 12 — A C51% 39% 30 B A B A Example 9 41 2.3 16 — A B 53% 41% 30 B B B A Example10 72 2.4 15 — A C 54% 43% 30 B A B A Example 11 62 2.4 15 — A C 53% 43%30 B B B A Example 12 75 3.2 10 — A C 49% 40% 30 B A A A Example 13 322.1 31 — A B 59% 51% 20 B B B A Example 14 52 2.5 12 — A B 58% 30% 40 BA B A Example 15 38 2.3 18 A B 59% 48% 20 B B B A Example 16 31 2.1 23 AB 62% 50% 20 B B B A Example 17 55 3 22 A B 59% 50% 20 A A B A Example18 51 3.3 19 A A 56% 51% 30 A B B A Example 19 44 2.5 23 A B 56% 49% 30A A B A Example 20 48 4.8 22 6 A A 58% 52% 20 A B A A Example 21 28 1.821 A B 52% 44% 30 B B B A Example 22 63 4.2 28 A B 55% 49% 30 B B B AExample 23 44 2.9 26 A B 60% 43% 30 B B B A Example 24 77 5.1 31 A B 52%52% 20 B A A A Example 25 34 2.6 26 A B 51% 41% 30 B B B A Example 26 422.6 27 A B 62% 48% 20 B B B A Example 27 38 2.7 18 A B 52% 29% 40 B B BA Example 28 38 3.5 21 A B 53% 36% 30 B B B A Example 29 41 3 26 A B 55%42% 30 B B B A Example 30 44 3 22 A B 58% 41% 30 B A A A Example 31 473.5 25 A B 57% 48% 20 B A A A Comparative 52 3.5 B B 21% 12% 80 C B C AExample 1 Comparative 55 3.3 B B 36% 15% 50 B D C B Example 2Comparative 5.2 0.1 38 A B 60% 55% 30 B D D C Example 3 Comparative 1.20.1 0.2 C D 57% 45% 30 B D D C Example 4 Comparative 0 0 0 C — 38% — — BD D C Example 5

TABLE 6 Content Primary Throwing Difference of Element Rust ObservationPower (%) in Coating Appearance Zr Si Sn Cu Prevention of sludge 210 V160 V Voltage (V) of Coating SDT CCT SST Example 32 42 3.2 18 A B 6900%6100% 10 A A A A Example 33 45 3.3 16 A B 6200% 5700% 20 A A A A Example34 41 3 15 A B 6200% 5500% 20 A A A A Example 35 38 2.9 16 A B 6400%5100% 30 A A A A Example 36 44 3.1 19 A B 6100% 5300% 30 A A A A Example37 51 3.6 21 A B 5900% 5200% 30 A A A A Example 38 48 3.5 16 A B 6000%4700% 30 A A A A Example 39 42 32 22 A B 6000% 4600% 20 A A A A Example40 55 3.8 18 8 A B 6900% 6200% 10 A A A A Example 41 48 18 8 A B 6800%6500% 10 A A A A Example 42 41 16 A B 6500% 6000% 20 A B B A Example 4352 17 7 A B 6500% 6000% 20 A B A A Example 44 43 18 A B 6200% 5500% 30 AB B A Example 45 55 18 9 A B 6000% 5600% 30 A B A A Example 46 43 16 A B5900% 5300% 30 A B B A Example 47 58 20 6 A B 6100% 4900% 30 A B A AExample 48 45 19 A B 6200% 4700% 30 A B B A Example 49 56 17 7 A B 5800%4400% 40 A B A A Example 50 41 16 A B 5800% 4500% 40 A B B A

TABLE 7 Primary Throwing Difference Appearance Content of Element RustObservation Power (%) in Coating of Zr Si Sn Cu Prevention of sludge 210V 160 V Voltage (V) Coating SDT CCT SST Example 51 91 5.7 19 A B 6200%5500% 30 A A A A Example 52 75 5.1 21 A B 5700% 5000% 30 A A A A Example53 81 5.3 18 A B 5600% 5100% 30 A A A A Example 54 88 5.7 14 A B 5900%4700% 30 A A A A Example 55 72 4.8 17 A B 6000% 5000% 30 A A A A Example56 72 18 6 A B 5900% 5100% 20 A B B A Example 57 85 21 A B 5700% 4800%30 A B B A Example 58 91 20 7 A B 5900% 5100% 20 A B B A Example 59 9418 A B 6000% 5200% 30 A B B A Example 60 44 3.2 15 A B 6200% 5500% 30 AA A A Example 61 46 3.1 19 A B 6100% 5100% 30 A A A A Example 62 49 3.618 A B 6000% 5300% 30 A A A A Example 63 38 3 20 A B 6500% 5700% 20 A AA A Example 64 44 3.2 16 A B 6600% 5500% 20 A A A A Example 65 41 3.5 17A B 6100% 5800% 20 A A A A Example 66 49 3.2 16 A B 6200% 5500% 30 A A AA Example 67 41 3.2 15 7 A B 6800% 5900% 20 A A A A Example 68 51 18 7 AB 5900% 5300% 30 A B A A Example 69 52 18 5 A B 6300% 5100% 30 A B A AExample 70 48 19 9 A B 6100% 5300% 30 A B A A Example 71 55 17 6 A B6500% 5500% 30 A B A A Example 72 43 16 10 A B 6200% 5800% 20 A B A AExample 73 49 20 7 A B 6600% 5400% 20 A B A A Example 74 52 17 5 A B6200% 5200% 30 A B A A Example 75 67 4.7 18 A B 5900% 5200% 30 A A A AExample 76 54 3.2 16 A B 6200% 5800% 20 A A A A Example 77 48 2.8 17 A B5900% 5000% 30 A A A A Comparative 58 4.2 B B 2200% 1000% 80 C B D BExample 6

TABLE 8 Content of Primary Throwing Difference Appearance Element RustObservation Power (%) in Coating of Zr Si Sn Cu Prevention of sludge 210V 160 V Voltage (V) Coating SDT CCT SST Example 78 55 13 A B 5800% 5000%40 B C B B Example 79 44 24 A B 5800% 2500% 40 B C B B Example 80 49 21A B 6900% 5500% 30 A C A B Example 81 45 18 A B 5900% 5000% 20 A C A BExample 82 38 26 A B 6000% 5000% 20 A C A B Example 83 45 9 A B 5900%5100% 20 A C A B Example 84 51 18 A B 5800% 5200% 20 A C A B Example 8543 21 A B 6000% 5400% 20 A C A B Example 86 36 18 A B 6100% 5300% 10 A CA B Example 87 47 23 A B 5900% 5100% 10 A C A B Example 88 32 33 A B6000% 5300% 20 A C A B Example 89 52 12 A B 6100% 5300% 20 A C A BExample 90 42 21 A B 6000% 5100% 20 A C A B Example 91 36 28 A B 5900%5300% 20 A C A B Example 92 50 22 A B 6000% 5100% 30 A C B B Example 9350 24 A A 5500% 4800% 30 B C B B Example 94 46 26 A B 5800% 4900% 30 B CB B Example 95 46 15 A A 6000% 5100% 20 A C A B Example 96 30 21 A B5600% 4800% 40 B C B B Example 97 65 26 A B 5700% 4700% 30 A C B BExample 98 42 19 A B 5300% 5000% 30 A C B B Example 99 72 21 A B 5200%4900% 30 A C B B Example 100 33 10 A B 5600% 3200% 40 B C B B Example101 43 22 A B 5200% 5200% 20 A C B B Example 102 40 24 A B 5800% 4200%20 A C B B Example 103 43 16 A B 5700% 4800% 30 B C B B Example 104 4117 A B 5400% 3400% 30 A C B B Example 105 40 21 A B 5700% 3300% 30 A C BB Example 106 40 11 A B 5500% 4500% 30 A C B B

INDUSTRIAL APPLICABILITY

The metal surface treatment liquid for cation electrodeposition coatingof the present invention is applicable to metal base materials, such asautomobile bodies and parts to be subjected to cation electrodeposition.

1-13. (canceled)
 14. A metal surface treatment liquid for cationelectrodeposition coating comprising zirconium ions and tin ions, andhaving a pH of 1.5 to 6.5, wherein: a concentration of zirconium ions isin the range of 10 to 10,000 ppm; and a concentration ratio of the tinions to the zirconium ions is in the range of 0.005 to 1 on a massbasis.
 15. A metal surface treatment liquid for cation electrodepositioncoating according to claim 14 further comprising a polyamine compound.16. A metal surface treatment liquid for cation electrodepositioncoating according to claim 15 wherein said polyamine compound is acondensate of aminosilane hydrolysate.
 17. A metal surface treatmentliquid for cation electrodeposition coating according to claim 14,further comprising copper ions.
 18. A metal surface treatment liquid forcation electrodeposition coating according to claim 15, furthercomprising copper ions.
 19. A metal surface treatment liquid for cationelectrodeposition coating according to claim 14, further comprisingfluorine ions, wherein the amount of free fluorine ions at a pH of 3.0is in the range of 0.1 to 50 ppm.
 20. A metal surface treatment liquidfor cation electrodeposition coating according to claim 14, furthercomprising a chelate compound.
 21. A metal surface treatment liquid forcation electrodeposition coating according to claim 20, wherein thechelate compound is sulfonic acid.
 22. A metal surface treatment liquidfor cation electrodeposition coating according to claim 14, furthercomprising an oxidizing agent.
 23. A metal surface treatment liquid forcation electrodeposition coating according to claim 14, furthercontaining nitric acid, wherein the concentration of said nitric acid isin the range of 100 ppm to 100000 ppm.
 24. A metal surface treatmentliquid for cation electrodeposition coating according to claim 14,further comprising at least one ion selected from the group consistingof aluminum ions and indium ions.
 25. A metal surface treatment liquidfor cation electrodeposition coating according to claim 15, furthercomprising at least one ion selected from the group consisting ofaluminum ions and indium ions.
 26. A metal surface treatment liquid forcation electrodeposition coating according to claim 16, furthercomprising at least one ion selected from the group consisting ofaluminum ions and indium ions.
 27. A metal surface treatment liquid forcation electrodeposition coating according to claim 23, furthercomprising at least one ion selected from the group consisting ofaluminum ions and indium ions.
 28. A method of metal surface treatmentcomprising a step of subjecting a metal base material to a surfacetreatment with the metal surface treatment liquid for cationelectrodeposition coating according to claim
 14. 29. A metal basematerial comprising a coating film formed by a surface treatmentobtained by the method according to claim
 28. 30. A metal base materialaccording to claim 29, wherein an element ratio of zirconium/tin on amass basis in the coating film is in the range of 1/10 to 10/1.
 31. Amethod of cation electrodeposition coating comprising steps of:subjecting a metal base material to a surface treatment with the metalsurface treatment liquid according to claim 14, and to washing withwater; and subjecting the surface treated metal base material to cationelectrodeposition coating.
 32. A metal base material coated by thecation electrodeposition obtained with the method according to claim 31.